Shoring systems are used to prevent walls of open excavations to cave in and secure the safety of working place. This invention relates to a particular type of shoring devices called ‘Slide Rail Shoring System’ consisting of rails, large shoring panels and horizontal struts or strutting assemblies. Each rail has laterally, on either side, one or more guides for sliding shoring panels. According to alignment of lateral guides on either side of the rail two distinct types of rails are specified, linear rail and corner rail. Panels sliding on either side of a linear rail follow same alignment forming conjointly a straight shoring wall. Panels sliding within one side of a corner rail are perpendicular to panels sliding within other side, outlining a 90 degrees turn of shoring wall. The linear rail has a frontal guide relative to interior of excavation, for sliding at least one horizontal strut or a strutting assembly. Linear rails are used in pairs, which are spaced apart along the excavation. Linear rails of a pair of rails are held vertically parallel and pressed against either wall of excavation by at least one horizontal strut or strutting assembly. Shoring panels slide within respective guides of adjacent linear rails of pair of rails creating thereby a stepped shoring wall. The outermost and innermost steps of the shoring wall relative to interior of excavation are called respectively outer wall and inner wall, so the lateral guides on either side of the rail. Corner rails are used on each corner of a rectangular shaped open excavation.
Previous slide rail shoring systems as disclosed in U.S. Pat. Nos. 3,910,053 and 4,657,442 (Krings), use rails having laterally individual formlocking channel guides of C-shaped section that interlock the guide edge of T-shaped section provided alongside each lateral end of shoring panels. This type of interlocking highly concentrates the stresses in the contact between rail and panel engendering damages in both rail and panels, strongly limiting the successful use of this shoring device.
The U.S. Pat. Nos. 5,310,289 and 5,503,504 (Hess et al.), disclose a rail having laterally on either side only one channel guide for both inner and outer walls, created respectively by an inner panel and an outer panel named according to the shoring wall they create. The channel guide has a U-shape and has on backside of the guide channel a square bar to interlock the outer panel within the rail. The guide edge of inner panel is not interlocked within rail and slides freely within presenting thereby a risk to kick in the trench when adjacent rails are not aplomb, what becomes a serious safety issue when depth of excavation is over 20 ft. deep. The outer and inner panels have unequal design and are not interchangeable raising inventory concerns in term of panel inventory, their handling and administration as well as various inconveniences during installation and removal of shoring system in job site.
U.S. Pat. Nos. 6,164,874 (May) discloses a slide rail shoring system as improvement or ulterior development of those published in U.S. Pat. Nos. 5,310,289 (Hess) and European Pat. Nos. 0 100 083 (May). Likewise, this shoring system uses two unequal types of shoring panels, an outer panel, which slides formlockingly within rail, and an inner panel, which slides freely within rail. This slide rail shoring system manifests same functionality and drawbacks as per those discussed previously above.